Rendezvous/src/FinalFactory.Rendezvous.Server/Provisioning/PublisherAuthorizationService.cs

using FinalFactory.Rendezvous.Contracts;

namespace FinalFactory.Rendezvous.Server.Provisioning;

internal sealed class PublisherAuthorizationService(GamePolicyRegistry policies)
{
    public PublisherAuthorizationResult Authorize(
        AuthenticatedPrincipal principal,
        GameId requestedGameId,
        EnvironmentId requestedEnvironmentId,
        RegionId requestedRegionId,
        uint requestedProtocolVersion,
        ListingVisibility requestedVisibility,
        IReadOnlyDictionary<string, string> requestedMetadata,
        DateTimeOffset now)
    {
        if (principal.ExpiresAt <= now)
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.PrincipalExpired);
        }

        if (principal is not IPublisherPrincipal publisher)
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.NotPublisher);
        }

        if (publisher.GameId != requestedGameId
            || publisher.EnvironmentId != requestedEnvironmentId)
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.ScopeMismatch);
        }

        if (!policies.TryGet(publisher.GameId, publisher.EnvironmentId, out GamePolicy? policy)
            || policy is null)
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.PolicyNotFound);
        }

        if (!policy.AllowsPublisherTrust(publisher.TrustMode))
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.TrustModeNotAllowed);
        }

        if (!publisher.AllowedRegions.Contains(requestedRegionId)
            || !policy.AllowsRegion(requestedRegionId))
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.RegionNotAllowed);
        }

        if (!policy.AllowsProtocol(requestedProtocolVersion))
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.ProtocolNotAllowed);
        }

        if (publisher.TrustMode == PublisherTrustMode.AnonymousUnlisted
            && requestedVisibility != ListingVisibility.Unlisted)
        {
            return PublisherAuthorizationResult.Denied(
                PublisherAuthorizationError.AnonymousMustBeUnlisted);
        }

        if (!policy.AllowsVisibility(requestedVisibility))
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.VisibilityNotAllowed);
        }

        if (!policy.AllowsMetadata(requestedMetadata))
        {
            return PublisherAuthorizationResult.Denied(PublisherAuthorizationError.MetadataNotAllowed);
        }

        return PublisherAuthorizationResult.Allowed(new AuthorizedPublisherContext(
            publisher.Subject,
            publisher.GameId,
            publisher.EnvironmentId,
            requestedRegionId,
            requestedProtocolVersion,
            requestedVisibility,
            publisher.TrustMode,
            policy));
    }
}

internal sealed record AuthorizedPublisherContext(
    string Subject,
    GameId GameId,
    EnvironmentId EnvironmentId,
    RegionId RegionId,
    uint ProtocolVersion,
    ListingVisibility Visibility,
    PublisherTrustMode TrustMode,
    GamePolicy Policy);

internal readonly record struct PublisherAuthorizationResult(
    bool IsAllowed,
    PublisherAuthorizationError Error,
    AuthorizedPublisherContext? Context)
{
    public static PublisherAuthorizationResult Allowed(AuthorizedPublisherContext context) =>
        new(true, PublisherAuthorizationError.None, context);

    public static PublisherAuthorizationResult Denied(PublisherAuthorizationError error) =>
        new(false, error, null);
}

internal enum PublisherAuthorizationError
{
    None = 0,
    NotPublisher = 1,
    ScopeMismatch = 2,
    PolicyNotFound = 3,
    TrustModeNotAllowed = 4,
    RegionNotAllowed = 5,
    ProtocolNotAllowed = 6,
    AnonymousMustBeUnlisted = 7,
    VisibilityNotAllowed = 8,
    MetadataNotAllowed = 9,
    PrincipalExpired = 10,
}